Variable valve actuation

ABSTRACT

A variable valve actuation mechanism actuates a valve of an internal combustion engine. The mechanism includes an actuator with a housing and a piston each moveable along a longitudinal axis in the engine. A cavity is defined between the piston and the housing. A body of fluid is disposed in the cavity and in the reservoir. A fluid passage has an open position wherein the cavity and reservoir are in fluid communication and a closed position wherein the cavity is sealed. When the passage is closed, the housing and piston move generally together. When the passage is open, fluid may pass from the cavity to the reservoir and movement of the housing relative to the piston changes the volume of the cavity.

REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/773,090, filed Feb. 14, 2006, the entire contentof which is incorporated herein by reference.

FIELD OF THE INVENTION

The invention relates to internal combustion engines. More particularly,the invention relates to a variable valve actuation mechanism forinternal combustion engines.

BACKGROUND OF THE INVENTION

Internal combustion (“IC”) engines are widely used for providingmechanical power to drive a variety of device. IC engines typicallyinclude a cylinder in which a fuel/air mixture is ignited, a pistonmovable in a reciprocating manner within the cylinder due to forcescreated by the ignition of the fuel/air mixture, and an output shaftdriven by the reciprocating motion of the piston. IC engines alsotypically include a valve assembly for controlling the intake offuel/air and exhaust of combustion products. The valve assembly is timedfor appropriate intake and exhaust during the intake, compression, powerand exhaust cycles of the engine. Variable valve actuation mechanismsare known for varying the timing of the valve assembly, yet it remainsdesirable to provide an improved variable valve actuating mechanism thatprovides enhanced performance, cost, and reliability over conventionaldesigns.

SUMMARY OF THE INVENTION

A variable valve actuation mechanism is provided for actuating a valveof an internal combustion engine. The variable valve actuation mechanismincludes an actuator having a housing and a piston each moveable along alongitudinal axis in the engine for actuating the valve. A cavity isdefined between the piston and the housing. The mechanism also includesa reservoir and a body of fluid disposed in the cavity and in thereservoir. A fluid passage has an open position wherein the cavity andthe reservoir are in fluid communication and a closed position whereinthe cavity is sealed. When the passage is closed and the cavity issealed, the housing and the piston move generally together. When thepassage is opened, fluid may pass from the cavity to the reservoir andmovement of the housing relative to the piston changes the volume of thecavity. Additional embodiments of the invention are also described andillustrated.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated as thesame becomes better understood by reference to the following detaileddescription when considered in connection with the accompanyingdrawings, wherein:

FIG. 1 is a cross-sectional view of portions of a variable valveactuation mechanism according to the present invention in a firstposition;

FIG. 2 is a cross-sectional view of the mechanism of FIG. 1 moved into asecond position;

FIG. 3 is a cross-sectional view of the mechanism of FIGS. 1 and 2shifted into a third position;

FIG. 4 is a cross-sectional view of portions of a variable valveactuation mechanism according to a second embodiment of the presentinvention with a cam lobe in a first position;

FIG. 5 is a view similar to FIG. 4 with the cam rotated to a secondposition;

FIG. 6 is a view similar to FIGS. 4 and 5 with the cam rotated to athird position;

FIG. 7 is a view similar to FIGS. 4-6 with the cam rotated to a fourthposition;

FIG. 8 is a view similar to FIGS. 4-7 with the cam rotated to a fifthposition;

FIG. 9 is a view similar to FIGS. 4-8 with the cam rotated to a sixthposition;

FIG. 10 is a view similar to FIGS. 4-9 with the cam rotated to a seventhposition;

FIG. 11 is a view similar to FIGS. 4-10 with the cam rotated to a eighthposition;

FIG. 12 is a view similar to FIGS. 4-11 with the cam rotated to a ninthposition;

FIG. 13 is a view similar to FIGS. 4-12 with the cam rotated to a tenthposition;

FIG. 14 is a cross-sectional view of portions of a variable valveactuation mechanism according to the a third embodiment of the presentinvention;

FIG. 15 is a view similar to FIG. 14, with the fluid removed from theillustration;

FIG. 16 is a view similar to the view of FIGS. 14 and 15 wherein thehousing is not cut away;

FIG. 17 is a view similar to FIGS. 14-16 wherein the housing is removedfrom the support;

FIG. 18 is a cross-sectional view of portions of a variable valveactuation mechanism according to a fourth embodiment of the presentinvention;

FIG. 19 is a view similar to FIG. 18 with the fluid removed;

FIG. 20 is a view similar to FIGS. 18 and 19 wherein the housing is notcut away;

FIG. 21 is a view similar to FIGS. 18-20 with the housing removed fromthe support; and

FIG. 22 is a view of a variable valve actuation system.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides various embodiments of a mechanism foractuating the valves of an internal combustion engine. The mechanism maytake the place of a typical mechanical or roller tappet or lifter, ormay be used in other ways. The illustrated embodiments, discussed below,are in the form of a roller lifter. Generally, the various embodimentsof the present invention include an actuator with a housing and a pistonthat define a first input end and a second output end of the actuator. Afluid cavity is defined between the piston and the housing, with thecavity being filled with a generally incompressible fluid. Depending onthe embodiment and the method of operation, the amount of fluid in thecavity may be increased, thereby increasing the size of the cavity andthe distance between the input and output ends of the actuator, may bedecreased, thereby reducing the size of the cavity and the distancebetween the ends, or the fluid may be trapped thereby forcing thehousing and piston to move as a unit Addition of fluid to the cavity maybe accomplished through the supply of pressurized fluid, such as engineoil. The amount of fluid in the cavity may be decreased by allowing thefluid to pass out of the cavity while a load is applied to the actuator,or the fluid may be pumped out. The cavity may be closed off such thatfluid is trapped such as by closing or blocking fluid passages thatwould otherwise be in fluid communication with the cavity.

By positioning the variable actuator between an input device, such as aneccentric lobe on a cam, and an output device such as a pushrod in avalve train, the actuator may be used to vary how much of the inputmotion is provided to the output device. One application of thisactuator is to vary the valve lift of engine intake and/or exhaustvalves.

FIGS. 1-3 illustrate a first embodiment of an actuator according to thepresent invention. These Figures illustrate an eccentric cam lobe 10which serves as in input device. The cam lobe is rotatable about arotational axis 12. Unlike a typical cam, the rotational axis 10 of thecam shaft 14 supporting the lobe 10 can be displaced in an off-axis orlateral direction to vary the midpoint of travel of the actuators 20 and22 that are in mechanical communication with the cam lobe 10. Each ofFIGS. 1-3 illustrate a different position of the rotational axis 12 anda resulting starting position of the cam lobe 10 and actuators 20 and22. The present invention may be used in a variety of applications. Theembodiment shown in FIGS. 1-3 is a design for use in a barrel enginewith a central drive shaft and cam shaft, which actuates tappets thatextend generally radially outwardly therefrom. An exemplary engine andvalve train is shown in pending PCT application serial numberPCT/US2006/024591, the entire contents of which is incorporated hereinby reference. Actuators 20 and 22 illustrate just two of the multipleactuators or tappets that may extend radially outwardly from a singlecam. In alternative embodiments, tappets or actuators may only extend inone direction from a cam.

The actuators 20 and 22 are substantially identical, and therefore onlyactuator 22 will be described in detail. The actuator 22 is disposed andsupported in hole 24 in a tappet carrier, engine block, or other support26, which may or may not form part of the actuator itself. The hole 24is preferably generally cylindrical. The actuator includes a housing 28and a piston 30 that are spaced apart so as to define a fluid cavity 32therebetween. The housing 28 has a first end 34 including a roller 36that serves as a bearing member for contacting the cam lobe 10. Thehousing has an opposite second end 38 with a generally cylindrical body40 extending therebetween. The cylindrical body is slidably received inthe cylindrical support hole 24 for movement along a longitudinal axisof the hole. The piston 30 is also generally cylindrical and slidablyreceived in the hole 24 for movement along the longitudinal axis. Theactuator 22 may be said to have a first input end defined by the roller36 and a second output end defined by the piston 30.

A biasing member 42 is preferably disposed in the cavity 32 and biasesthe housing 28 and the piston 30 away from each other. The cavity 32between the housing 28 and piston 30 is filled with an incompressiblefluid, such as engine oil. At least one outlet 44 is provided in thesupport 26 for allowing fluid to enter or exit the cavity between thehousing 28 and piston 30.

Three movement zones for the actuator 22 are labeled as a slosh area,between lines C and A, a squish area between lines A and B, and a liftarea between lines B and D. Referring to FIG. 1, the cam shaft 14 isillustrated in a position most distant from the support 26. The cam lobehas a lift portion 11 wherein the surface of the lobe is most distantfrom the axis of rotation 12. As will be clear to those of skill in theart, rotation of the cam lobe 10 in the position shown in FIG. 1 willresult in movement of the housing 28 in the “slosh” area defined betweenpoints C and A. Movement of the housing 28 in this region results insubstantially no movement of the piston 30, as fluid in the cavity 32 isdisplaced and replaced through the outlet 44. As the housing 28 is movedin the slosh area towards the piston 30, the fluid leaks or is squeezedout through the outlet 44. As the housing moves away from the piston, inthe slosh area, fluid is preferably provided through the outlet 44. Ifthe fluid in the outlet 44 is pressurized, fluid will flow from thecavity into the outlet when the pressure in the cavity exceeds thepressure in the outlet 44, such as when the cam lobe is forcing thehousing 28 toward the piston. When the force of the lobe is removed,when it rotates to a lower lift position, the biasing member will biasthe housing toward the cam and the pressure in the cavity will fallbelow the pressure in the outlet, and fluid will again fill the cavity.In this situation, the valve being driven by the actuator 22 will bemostly or completely deactivated. The outlet 44 may be considered to bepart of or in fluid communication with a reservoir of fluid and/or apressurized supply of oil in an engine.

In FIG. 2, the cam shaft 14 and cam lobe 10 are shifted transverselytoward the support 26 and actuator 22 relative to the position shown inFIG. 1. In this position, rotation of the cam shaft 14 about the axis 12causes reciprocal movement of the housing 28 within the slosh, squishand “lift” areas. There is substantially no movement of the piston 30until the housing 28 is moved beyond the end of the squish area at lineB and into the lift area. Once the second end 38 of the housing passesline B, the cavity is sealed or cut off from the outlet 44 and thereforethe piston 30 and housing 28 move together. The outlet may be consideredpart of a passage that may be open, as shown in FIG. 1, or closed, as inFIGS. 2 and 3. In the open position, there is fluid communicationbetween the cavity and a reservoir of fluid, and in the closed positionthe reservoir is sealed off.

In the lift area, displacement of the housing 28 toward the piston 30causes compression of the fluid therebetween, thereby causingdisplacement of the piston 30 with the housing 28. It should be notedthat the fluid is preferably substantially incompressible. As such,compression of the fluid does not cause a reduction in the volume of thecavity but instead merely transfers force from the housing to thepiston. Shifting the cam shaft 14 and cam lobe 10 in this manner changesthe midpoint of travel for the housing 28 and consequently the motionprofile for the piston 30 and valve train. Shifting the midpoint oftravel toward the actuator 22 shortens the maximum distance between thesecond end 38 of the housing 28 and line B. Thus, shifting the midpointof travel toward the actuator 22 minimizes the delay associated with thedisplacement of fluid through the outlet 44.

In FIG. 3, the cam shaft 14 is shifted more toward the actuator 22resulting in the housing 120 moving within only the lift or in thesquish and lift areas. Thus, movement of the housing 28 results insubstantially full actuation of the piston 30 and valve train. The camshaft 14 and cam lobe 10 can be shifted by any suitable mechanisms knownby those having ordinary skill in the art, such as by hydraulic orelectric motorized actuators. It should also be appreciated by thoseskilled in the art that the transverse movement of the cam shaft 14shown in FIGS. 1-3 is applicable to the other embodiments describedherein.

While the piston 28 and housing 30 are illustrated as being spaced apartand not in mechanical contact, an alternative embodiment provides ahousing that has a bore defined therein and the piston is received inthe bore. The fluid filled cavity is defined in the bore between thepiston and the housing. A passage similar to passage 44 may beselectively in fluid communication with the cavity depending on theposition of the housing relative to a support. The housing may provide atravel limit for the piston such that the piston cannot be move out ofthe bore.

Referring to FIGS. 4-13, another alternative actuation mechanism foractuating a valve of an internal combustion engine is generallyindicated at 110. The mechanism 110 includes a tappet housing 120, apiston 140, a biasing member 150 and a bearing member 160.

The tappet sleeve or housing 120 is slidably supported in a cylindricalhole 122 formed in a roller tappet carrier supported in an engine blockor formed in the engine block itself. The housing 120 is cylindricallyshaped. A bore 124 is formed in one end of the housing 120 for slidablyreceiving the piston 140 therein. A fluid cavity is formed in thehousing 120. A portion of the fluid cavity is defined by an annular slot126 and a center bore 128. Both the annular slot 126 and center bore 128are formed in an end wall of the housing 120. The center bore 28 isgenerally concentric with the slot 126. A middle section 130 of thehousing 120 has a reduced outer diameter relative to the ends. Anannular space 132 is defined between the middle section 130 and thewalls defining the hole 122 due to the reduced diameter of the middlesection 130. A reservoir 134 is continuous with the annular space 132,slot 126 and bore 128 so that fluid can pass freely therebetween. Agenerally incompressible fluid is disposed in the slot 126, bore 128,annular space 132 and reservoir 134. The reservoir may take the form ofa pressurized supply of fluid, such as an oil supply in an engine or maybe in fluid communication therewith.

Preferably, each of the systems illustrated herein has a fluid reservoirin fluid communication with the cavity such that fluid may pass quicklyback and forth between the cavity and reservoir. As will be clear tothose of skill in the art, energy loss may be minimized by positioningthe reservoir nearby and/or provided a large passage between the cavityand reservoir. It is also preferred that the reservoir have an air orgas chamber therein, as illustrated, with the gas chamber serving as anair or gas spring. It is preferred that the cavity and reservoir also bein fluid communication with a lubrication system such as a pressurizedoiling system.

The piston 140 includes a head 142 slidably supported in the bore 124 ofthe housing 120. The head 142 is cylindrically shaped. The head 142includes an annular groove 144 for receiving and supporting a lubricantfor minimizing friction between the piston 140 and the housing 120.Optionally, the annular groove 144 supports an annular gasket. A rod 146extends outwardly from one end of the head 142 toward the end wall ofthe bore 124. The rod 146 is axially aligned with the center bore 128. Avalve or valve actuation mechanism in the form of a pushrod and/orrocker arm is operatively coupled with the opposite end of the head 142,so that the valve is actuated by movement of the piston 140.

A recess 131 is formed in the opposite end of the housing 120 forreceiving the bearing member 160 therein. The bearing member 160 isprovided in the form of a roller. The bearing member 160 is pivotallycoupled to the housing 120 and received in the recess 131. A portion ofthe bearing member 160 protrudes outwardly from the recess 131 forrollingly engaging an eccentric cam lobe 170. The cam lobe 170 isrotatably driven by a cam shaft 180 for rotation about an axis 182 ofthe cam shaft 180. It should be appreciated that the components shown inthe figures may not be to scale and the profile of the cam lobe 170 maybe different than shown.

The biasing member 150 is provided in the form of a helical spring,which maintains the bearing member 160 in contact with the cam lobe 170.Optionally, the biasing member 150 includes a plurality of springs forbiasing the bearing member 160 toward the cam lobe 170.

In use, the cam lobe 170 is driven by the engine via the cam shaft 80.The bearing member 160 rolls along the outer eccentric surface of thecam lobe 170, thereby causing reciprocating movement of the housing 120relative to the hole 122. As shown by the sequence of FIGS. 4-9,counterclockwise rotation of the cam lobe 170 causes axial displacementof the housing 120 toward the piston 140. The rod 146 moves toward thecenter bore 128. Fluid is displaced into the reservoir 134. Movement ofthe housing 120 does not cause displacement of the piston 140 untilfluid becomes trapped between the rod 146 and the bore 128, which occursstarting with FIG. 7. Due to the incompressible nature of the fluid,continued axial displacement of the housing 120 in the up direction inFIG. 9 causes movement of the piston 140 therewith. While FIGS. 7-11illustrate the lower end of the rod 146 stopping at the top of the bore128, in practice the rod may protrude somewhat into the bore dependingon the clearances and the time that the rod is adjacent the bore. InFIGS. 10-13, the bearing member 160 rolls beyond the high point of thecam lobe 170, so that the housing 120 moves downwardly in the directionof the cam shaft 180. The piston 140 follows the housing 120 downwardlyuntil FIGS. 12-13, wherein the valve is closed. At this point, thebiasing member 150 biases the housing 120 and the piston 140 apart fromeach other, thereby maintaining the bearing member 160 in contact withthe cam lobe 170. Fluid is drawn from the reservoir to fill the bore 128as the rod 146 is withdrawn from the bore 128.

Thus, rotation of the cam lobe 170 about the axis of the cam shaft 180causes reciprocal movement of the housing 120 along the axis of the hole122. The piston 140 reciprocates with the housing 120, although initialmovement of the housing 120 is lost relative to the piston 140 due tothe need to first displace fluid from and compress the remaining fluidbetween the bore 128 with the rod 146. The reciprocal movement of thepiston 140 causes actuation of the valve via engagement between thepiston head 140 with the valve directly, or the rod or rocker armmechanically coupled therebetween.

A third embodiment of the invention is shown in FIGS. 14-17, wherein theslot and the bore of the prior embodiment are replaced by a single fluidcavity 228 formed in the housing 220. This third embodiment may operatelike the first embodiment, wherein an outlet 244 is provided which is inselective fluid communication with the cavity 228, depending on theposition of the housing 220. The outlet 244 may be part of or in fluidcommunication with a reservoir of fluid, such as a pressurized supply ofoil in an engine. FIG. 14 shows fluid filling the cavity 28, an annulararea 230 around the housing 220 and the outlet 244. FIG. 15 illustratesthe actuator without fluid. FIG. 16 illustrates the actuator wherein thehousing 220 is not cut away, and FIG. 17 shows the housing removed fromthe hole or support in the engine block. In the position illustrated inFIGS. 14 and 15, the reservoir 228 is cut off from the outlet 244 due tothe position of the housing relative to the outlet.

A fourth embodiment of the invention is shown in FIGS. 18-21, wherein aportion of the housing from the third embodiment is removed leaving onlyan end portion 320. The biasing member 350 is compressed between thepiston 340 and the end portion 320. The piston 340 is slidably supportedin the hole 322 in the engine block as in the first embodiment, ratherthan the bore of the housing as in the second embodiment. FIG. 18illustrates the actuator with fluid in the cavity 328 and outlet 344. Inthe position shown, the passage between the cavity 328 and outlet 344 isclosed. FIG. 19 illustrates the actuator with the fluid removed. FIG. 20illustrates the actuator wherein the end portion 320 is not cut away,and FIG. 21 illustrates the actuator by itself, without being in a holeof support.

Referring to FIG. 22, a variable valve actuation system is generallyillustrated at 400. The system includes a cam shaft 402 that isrotatable about a rotational axis. The cam shaft includes at least onelobe 404. A tappet carrier or other support 406 has a receiving area 422defined therein and receives a variable actuator according to anyembodiment of the present invention. The illustrated version includes ahousing 420, piston 440 and biasing member 450. One end of the actuatoris in mechanical communication with the cam lobe 404 and the other is inmechanical communication with a valve 460 via a valve train including arocker arm 462 and a pushrod 464. An opening 470 is defined in the innersurface of the support 406 and is in fluid communication with areservoir and/or fluid supply as discussed previously. The actuator hasan opening that is in fluid communication with the opening 470 in somepositions of the actuator. In the illustrated embodiment, the opening inthe actuator is the entire gap between the housing and piston, which isthe side of the cavity 480.

The invention has been described in an illustrative manner. It is,therefore, to be understood that the terminology used is intended to bein the nature of words of description rather than of limitation. Manymodifications and variations of the invention are possible in light ofthe above teachings. Thus, within the scope of the appended claims, theinvention may be practiced other than as specifically described.

1. A variable valve actuation mechanism for actuating a valve of aninternal combustion engine, the variable valve actuation mechanismcomprising: an actuator including a housing and a piston each movablealong a longitudinal axis in the engine for actuating the valve, acavity being defined between the piston and the housing; a reservoir; abody of fluid disposed in the cavity and in the reservoir; a fluidpassage having an open position wherein the cavity and the reservoir arein fluid communication and a closed position wherein the cavity issealed; wherein when the passage is closed and the cavity is sealed, thehousing and the piston move generally together; and wherein when thepassage is open, fluid may pass from the cavity to the reservoir, andmovement of the housing relative to the piston changes the volume of thecavity.
 2. A variable valve actuation mechanism according to claim 1,further including a biasing member disposed between the housing and thepiston, the biasing member biasing the housing and piston away from eachother.
 3. A variable valve actuation mechanism according to claim 1,wherein the reservoir comprises a pressurized supply of engine oil.
 4. Avariable valve actuation mechanism according to claim 1, wherein thereservoir is in fluid communication with a pressurized supply of engineoil.
 5. A variable valve actuation mechanism according to claim 1,wherein the reservoir is at least partially filled with a gas thatserves as a gas spring.
 6. A variable valve actuation mechanismaccording to claim 1, wherein the housing and the piston are bothgenerally cylindrical.
 7. A variable valve actuation mechanism accordingto claim 1, wherein the housing includes a roller for interaction with acam lobe.
 8. A variable valve actuation mechanism according to claim 1,wherein the housing has a bore defined therein, the piston beingslidably received in the bore.
 9. A variable valve actuation mechanismaccording to claim 1, wherein the bore in the housing and the piston areboth generally cylindrical.
 10. A variable valve actuation mechanismaccording to claim 1, further including a cam shaft with a cam loberotatable about a rotational axis, the cam lobe being in mechanicalcommunication with the housing for actuating the housing in areciprocating manner along the longitudinal axis, the cam being movablein a direction transverse to the rotational axis to cause acorresponding shift in the midpoint of travel of the housing.
 11. Avariable valve actuation system comprising: a cam shaft with a cam lobe,the shaft being rotatable about a rotational axis; a tappet support witha receiving area defined therein, the receiving area having an innersurface with a fluid supply opening defined therein; a fluid supply influid communication with the supply opening; a valve movable between anopen and a closed position; a variable valve actuator having a first anda second end, the actuator comprising; a housing defining the first endof the actuator; a piston defining the second end of the actuator; acavity defined between the housing and piston; the actuator having anouter surface with an opening defined therein, the opening being influid communication with the cavity, the actuator being received in thereceiving area with the outer surface of the actuator adjacent the innersurface of the receiving area; one of the ends of the actuator being inmechanical communication with the cam lobe and the other of the endsbeing in mechanical communication with the valve; the variable valveactuator having a first position wherein the opening in the outersurface is in fluid communication with the opening in the inner surfaceof the receiving area such that the cavity is in fluid communicationwith the fluid supply, wherein when the actuator is in the firstposition fluid may pass between the cavity and the supply such thatmovement of the housing relative to the piston changes the volume of thecavity; and the variable valve actuator having a second position whereinthe opening in the outer surface is not in fluid communication with theopening in the inner surface of the receiving area such that the cavityis sealed and the housing and piston move generally together
 12. Avariable valve actuation system according to claim 11, further includinga biasing member disposed between the housing and the piston of theactuator, the biasing member biasing the housing and piston away fromeach other.
 13. A variable valve actuation system according to claim 11,wherein the fluid supply comprises a pressurized supply of engine oil.14. A variable valve actuation system according to claim 11, wherein thefluid supply includes a reservoir.
 15. A variable valve actuation systemaccording to claim 14, wherein the reservoir is at least partiallyfilled with a gas that serves as a gas spring.
 16. A variable valveactuation system according to claim 11, wherein the housing and thepiston are both generally cylindrical.
 17. A variable valve actuationsystem according to claim 11, wherein the housing includes a roller forinteraction with the cam lobe.
 18. A variable valve actuation systemaccording to claim 11, wherein the housing has a bore defined therein,the piston being slidably received in the bore.
 19. A variable valveactuation system according to claim 11, wherein the bore in the housingand the piston are both generally cylindrical.